The present invention relates generally to methods and apparatuses for depositing films on partially fabricated integrated circuits (ICs). More specifically, the invention relates to methods and apparatuses for accelerating the deposition of certain materials from organometallic compounds.
In integrated circuit fabrication, various materials are deposited on a substrate at various stages in the fabrication process. By way of example, dielectric layers may be formed between metallization layers to enable the formation of multi-level connections to devices, to produce field oxide regions used to isolate semiconductor active devices, to produce passivation layers used to protect entire IC chips during packaging, and to form masks used in subsequent etching processes.
There are many well known techniques used for depositing dielectric materials such as silicon dioxide (SiO.sub.2). Such techniques often include the use of an organometallic reactant such as tetraethylorthosilicate "TEOS" Si(OC.sub.2 H.sub.5).sub.4. Such materials are introduced into a chemical vapor deposition (CVD) reactor chamber and there decomposed to form SiO.sub.2 films and by-products. TEOS is in a liquid state at room temperatures and must be heated in an external vaporizing apparatus or otherwise converted to the gas phase before being introduced into a CVD reactor chamber.
Although forming SiO.sub.2 films from TEOS is popular because generally good step coverage is provided and the required deposition temperatures are relatively low, TEOS is very expensive. Therefore, there is a need to utilize a high percentage of TEOS in producing SiO.sub.2 films (as opposed to being pumped out of the CVD reaction chamber as unused reactant).
At least three TEOS-based SiO.sub.2 deposition processes are now commonly used. These include plasma enhanced chemical vapor deposition--with oxygen (PECVD-O.sub.2), low pressure chemical vapor deposition--with oxygen (thermal LPCVD-O.sub.2), and atmospheric pressure chemical vapor deposition--with ozone (APCVD-O.sub.3). While the introduction of oxygen and ozone promotes TEOS decomposition, it has been found that the TEOS decomposition reaction is still quite slow and therefore causes significant problems. Notably, a relatively high fraction of the TEOS introduced into a CVD chamber goes unreacted and is therefore wasted. In addition, the relatively slow rate at which TEOS decomposes has been found to cause certain structural defects (e.g., voids) resulting from the deposition of TEOS SiO.sub.2 films over gaps between vertical structures.
By way of example, FIG. 1 is a cross-sectional view of a partially fabricated semiconductor device 100. A silicon substrate 101 is shown having a thin dielectric layer 102 deposited over silicon substrate 101. Any conventional method may be used to deposit dielectric layer 102. A metallization layer is then blanket deposited over dielectric layer 102 such that the entire surface is covered with metallization material. The metallization material is then patterned using conventional photolithography processes to define metallization lines 104 over dielectric layer 102. Next, a silicon dioxide film 106 is deposited by reaction of TEOS and O.sub.2 and/or O.sub.3 over metallization lines 104 and dielectric layer 102. As illustrated, a void 108 may form between the gap between metallization lines 104.
The formation voids 108 in between gaps may present various undesirable consequences. By way of example, when successive layers are formed over silicon dioxide film 106, the danger of structural support or micro-cracking may cause entire integrated circuit (IC) chips to become unusable.
It should also be noted that slow TEOS decomposition rates may also reduce IC throughput since wafers must sit in deposition chamber reactors for longer periods of time. Still further, slow TEOS decomposition may be associated with incomplete removal of carbon containing moieties which remain as contaminants in the deposited silicon dioxide films.
In view of the foregoing, it would be desirable to have a method and apparatus for depositing silicon dioxide films from TEOS by a reaction having increased TEOS decomposition rates to prevent the formation of voids in gaps, to increase the percentage of TEOS actually used to form silicon dioxide and to reduce carbon contamination of silicon dioxide films.